1. Field of the Invention
The present invention relates to a numerical controller and particularly relates to a numerical controller that has a cutting control function through turret rotation.
2. Description of the Related Art
In an ordinary lathe, having a straight axis (generally referred to as X axis) that makes a cutter move in radial directions with respect to a work, control over depth of cut is carried out through straight-line movement by the X axis. Meanwhile, machine tools preferably have small number of axes for reduction in costs and sizes. A cost reduction effect and/or a size reduction effect are obtained if the depth of cut can be controlled without use of a straight-line movement mechanism for the X axis and if the straight-line movement mechanism for the X axis can be omitted.
Prior art techniques in which the depth of cut is controlled by means other than the straight-line movement mechanism for the X axis include techniques disclosed in Japanese Patent No. 5287986 and Japanese Patent Application Laid-Open No. 2009-190157. In these techniques, cutting work is performed on a workpiece that does not rotate, by controlling a tool so that it revolves around the workpiece, an eccentric rotation part that holds the tool on a first rotation table is provided in addition to a spindle rotation part that faces a chuck which fixes the workpiece and that rotates as a spindle, and the depth of cut is controlled based on rotation control over the eccentric rotation part.
These techniques, however, are intended for machines of types in which the tool revolves around the fixed workpiece and the machines of such types have problems in that necessary tool change is troublesome because of impossibility to attach a plurality of tools thereto. On the other hand, a machine with a turret to which a plurality of tools can be attached is of a type in which a rotating workpiece is turning-machined by pressing a tool attached to the turret against the rotating workpiece and it is impossible to simply apply the techniques disclosed in Japanese Patent No. 5287986 and Japanese Patent Application Laid-Open No. 2009-190157 described above to the machines of the type.